Ask HN: What kind of “investment time” or “20% time” policy do you have?

Google has 20% time [0], thoughtbot has investment time [1], I'm wondering what other companies do along these lines? I'm especially curious how these kinds of policies work at the different stages of a start up company. [0] https://googleblog.blogspot.com/2006/05/googles-20-percent-time-in-action.html [1] https://playbook.thoughtbot.com/#investment